1. Field of the Invention
The present invention relates to transport of a picture, and more particularly, to a moving picture terminal and a method for using same that transports a still picture.
2. Background of the Related Art
As the multimedia communication era arrives, the moving picture terminal has been realized, and will be put into practical service in a near future. Such a moving picture terminal has an encoder and decoder for processing the moving picture for realtime transmission or reception of successive video frames. However, the moving picture terminal cannot transmit/receive a high quality still picture. Therefore, to transport a still picture to an opposite party, a digital camera, a scanner and a computer are used. That is, either the digital camera or the scanner is connected to the computer for transmission of the still picture.
A method for transmitting a still picture by using such as the digital camera, the scanner, and the computer will now be described. FIG. 1 illustrates a related art system for transmitting a still picture.
As shown in FIG. 1, a desired still picture is captured by using a digital camera 100, stored in a computer 102, and transported to an opposite party through a wire or wireless network. On the other hand, if there is no digital camera, a photograph of the object is taken using a conventional camera and scanned by a scanner 101 to capture the still picture. Then, the captured still picture is stored in the computer 102, and transported to the opposite party using the computer 102 through a wire or wireless network.
The encoder and decoder in the related art moving picture terminal will now be described. FIG. 2 illustrates a block diagram showing an encoder in the related art moving picture terminal, and FIG. 3 illustrates a block diagram showing a decoder in the related art moving picture terminal.
Referring to FIG. 2, the encoder in the related art moving picture terminal is provided with a core part 210 for receiving, compressing, and encoding successive picture frames, a VLC 230 and a channel buffer 240. The VLC 230 is for receiving symbols coded in the core part 210 and assigning short length codes to symbols with a high frequency of occurrence in view of probability and relatively long codes to symbols with a low frequency of occurrence for the symbols coded in the core part 210. The channel buffer 240 is for buffering and forwarding data from the VLC 230 and providing a buffer state to a transmission rate controller 201 in the core part 210.
The core part 210 is a DCT 200 for receiving and subjecting a picture data to discrete cosine transform, and a quantizer 202 for quantizing the picture data and providing same to the VLC 230 for compressing the picture frames. The transmission rate controller 201 is for controlling a transmission rate according to quantized values at the channel buffer 240. The core part 210 further includes an inverse quantizer 203 for inverse quantizing the data quantized at the quantizer 202 to restore original picture frames from the coded picture frames, an ICDT 204 for subjecting the DCT data from the inverse quantizer 203 to Inverse Discrete Cosine Transform (IDCT) and a frame memory 220 for storing frames of the picture data restored at the IDCT 204. A motion estimator 206 and a motion compensator 205 are for comparing a received frame and a prior frame, which is the frame stored in the frame memory, to estimate a difference of motions and for compensating the difference.
The operation of the related art encoder will now be described. After compressing input of successive picture frames by subjecting the picture frames to DCT at the DCT 200, the successive picture frames are encoded into a bitstream with different bit lengths at the VLC 230 via the quantizer 202, which discards high frequency terms. The coded bitstream is stored in the channel buffer 240, and transmitted toward the receiver side through a wireless network. In this instance, the channel buffer 240 provides an amount of transmitted data to the transmission rate controller 201, and the transmission rate controller 201 adaptively computes a quantizing value according to the amount of transmitted data and provides the quantizing value to the quantizer 202. Accordingly, a transmission rate of the data transmitted from the channel buffer 240 is controlled. During the above-described process, the core part 210 has the coded picture frames subjected to IDCT through the inverse quantizer 203 and the IDCT 204, to be restored into original picture frames that are stored in the frame memory 220, which can store pictures of one frame amount. The restored original frames are stored for computing a motion difference between incoming successive picture frames and prior picture frames. The motion difference is estimated according to correlation between adjacent picture frames at the motion estimator 206, and the difference is compensated at the motion compensator 205, for making a real time moving picture transmission available.
In this instance, to estimate and compensate for the difference of motions between the adjacent picture frames, at least a first frame of the incoming picture sequence should be coded only with its own frame regardless of the correlation with the adjacent frame. This method of coding is called as “I picture coding”, and a method of coding using a correlation with the adjacent frame is called as “P picture coding.”
The decoder shown in FIG. 3, which operates opposite to the encoder, will now be described. That is, after being restored into an original picture by subjecting the coded picture frame to inverse quantizing and IDCT at a decoder core part 270, the coded picture frame received through a channel buffer 250 and a VLC 260 is reproduced. The core 270 includes inverse quantizer 271, IDCT 272 and motion compensator 273. Similar to the encoder, the reproduced picture is stored in a frame memory 280, for reproducing the moving picture in realtime by using correlation with the picture frame received in succession.
As described above, the related art moving picture terminal has various disadvantages. First, due to a limitation in a channel bandwidth for realtime transmission of the moving picture, the related art moving picture terminal transmits pictures, not in high quality, but in a low quality when the picture is a moving picture that requires a realtime transmission. Accordingly, it is difficult to transmit a high quality still picture. Further, the transmission of a still picture using a digital camera, a scanner, and a computer requires these additional costly apparatuses that are also inconvenient and cumbersome to use. Thus, a need exists and ceaseless demands have been made for a moving picture terminal that can transmit, not only the moving picture, but also a high quality still picture.
The above references are incorporated by reference herein where appropriate for appropriate teachings of additional or alternative details, features and/or technical background.